1. Technical Field
The present invention relates to an ink composition and an image forming method.
2. Related Art
The ink jet recording method is a method in which ink droplets are caused to fly, and recording is performed by the droplets being attached to a recording medium. In recent years, an ink for ink jet recording has been developed able to realize the image quality of silver halide photography, even in a case in which normal paper is used as the recording medium. Further, in addition to various types of paper, there are coated papers coated with an ink absorbing layer or the like, plastic films, fabrics and the like as the recording medium (below, also referred to as “medium”), and inks suited to performing ink jet recording with respect to each of these media have also been developed.
Examples of an ordinary ink used in ink jet recording include aqueous inks in which the main component is water, and in which a coloring agent and various additives are contained. For example, a water-based ink composition with no bleeding and excellent glossiness with respect to a specialized paper due to using a polysiloxane compound as a surfactant and adding an alkane diol, such as 1,2-hexanediol, is disclosed in JP-A-2005-194500.
Meanwhile, in a case where the ink absorption capacity of the medium is poor, permeability of the ink into the recording medium is insufficient when a water-based pigment ink is used, and there are cases of unevenness in glossiness occurring in the image. In such cases, that unevenness in glossiness is able to be improved by using an ink composition using a polyether-modified polysiloxane-based compound as a surfactant with respect to a glossy medium is disclosed in, for example, JP-A-2004-210996.
Incidentally, in a case in which a solid image (image in which ink is coated all over) is formed on a recording medium using an ink jet recording method, there is a need for wetting and spreading properties of the ink on the recording medium. Further, in cases where the recording surface of the medium does not absorb ink, or absorbs almost no ink, or in cases where the ink has characteristics of easily cissing, it is important to sufficiently increase the wetting and spreading properties of the ink and suppress cissing.
On the other hand, in a case where a solid image is formed on a recording medium by an ink jet recording method, since the number of ink droplets to be attached is able to be decreased if the volume of each of the ink droplets ejected is increased, it is possible to reduce the number of scannings, and it is expected that the head resolution (density of nozzles arranged in the head) may not be that high. In addition, in this case, with regard to the wetting and spreading properties of the ink droplets on the recording medium, it is expected that the more the composition wets and spreads, the easier it is to form a solid image.
However, in a surfactant used in inks of the related art, in particular among the media, in media which absorb little ink (low absorbent), such as plastic films and the like, or do not absorb ink (non-absorbent), the action of increasing the wetting and spreading properties of ink on the medium are not necessarily sufficient. In addition, with a surfactant of the related art, when the volume of ink droplets ejected from the head is increased, cissing and the like of the ink on the medium often occurs.
In this way, in forming a solid image with respect to a low absorbent or non-absorbent medium, there is demand for an ink with broad performance in adhesiveness, drying properties, anti-cissing properties, wetting and spreading properties, and the like. As one means for conferring such characteristics to the ink, examples include changing the type or blending of surface active substances included in the ink, and there is a need for the properties of the various types in the ink to be balanced to a high degree, in this way.